JPS60118694A - Method for synthesizing diamond under low pressure - Google Patents

Abstract

PURPOSE:To produce diamond on a substrate with high productivity, by introducing a mixed gas of a hydrocarbon and hydrogen under a low pressure into a furnace in which a plasma is generated, activating the mixed gas with a heated thermionic emitting material, and bringing the activated mixed gas into contact with the heated substrate. CONSTITUTION:A substrate 2 is placed on a supporting table 3 provided in a reaction furnace 4 and heated at 300-1,100 deg.C, and a plasma is generated by high-frequency discharge between electrodes 6 provided below the substrate 2. A mixed gas of a hydrocarbon and hydrogen under 0.1-10 Torr pressure is introduced from an introductory pipe 9 into the reaction furnace 4, activated by a heated thermionic emitting material 1 and brought into contact with the heated substrate 2 to produce a diamond film on the substrate 2. Thus, the high-frequency plasma is generated in the reaction furnace 4, and the excitation state of the hydrocarbon and hydrogen can be maintained for a long time. Thus, the aimed diamond can be efficiently obtained.

Description

[Detailed Description of the Invention] This patent relates to improvements in a low-pressure diamond synthesis method.

Conventionally, diamond has been synthesized at high temperatures and pressures using catalysts such as iron group metals, especially N1, but this method is extremely expensive.

Therefore, research has begun on the synthesis of diamond by low-pressure methods, and the following methods are known.

l) Synthesize diamond by creating excited carbon through thermal decomposition using a thermionic emitting material.

2) Use plasma to synthesize diamond by exciting hydrocarbons with plasma.

3) Ion beam method in which an ion beam is generated at low pressure and collided with the substrate surface to release free carbon and convert the diamond into diamond. 4) As an excitation method, a microfluid is introduced to generate hydrocarbon water. However, either method However, at present, it has the drawbacks of being thick (・reaction zone cannot be achieved (・) and difficult to increase in size (・).

The thermal decomposition method of 1) is simple, but it requires a reaction.

It has the disadvantage that the zone is particularly small (・ru.

This may be due to the short lifetime of the activated states of hydrocarbons and hydrogen excited by the thermionic emitting material (or the optimum distance between the thermionic emitting material and the substrate for diamond formation). This is because this distance range (i.e., reaction zone) is narrowly focused on non-hunting.For this reason, it has been a major obstacle in industrialization, which requires a large reaction zone.

On the other hand, method (2) of generating plasma by applying high frequency waves to the outside or inside of the reactor and method (4) of generating plasma by introducing microwaves are both methods of generating plasma in the reactor. Is it difficult to uniformly control the condition of objects, especially those of various shapes such as tools and wear-resistant parts? When attempting to coat it, there is a problem in that it is difficult to obtain a uniform coating layer, and it has not yet reached the stage of industrialization.

In addition, method (3) has a slow deposition rate and tends to produce a film with an amorphous structure, and so far there has been no report that it has produced a clear diamond film.

In order to improve these problems, especially the shortcomings of the thermionic emitter method (1), the inventors of the present invention conducted extensive testing and found that
I found a way to solve the above problems.

That is, a mixed gas of hydrocarbons and hydrogen is introduced into a furnace in which plasma is generated in a device installed 1.5 parts behind the base support, heated to 1200°C or higher, and subjected to 4H for ≠ vapor phase synthesis. It was found that the reaction zone expanded more than 10 times in the case of the horn of the thermionic emitting material. The reason for this is clear (although it may not be a good idea, but it is probably due to the plasma extending the lifespan of hydrocarbon gas and hydrogen gas in an activated state).

Also, according to this method, the substrate is directly exposed to the plasma at a low temperature, so there is no problem caused by the non-uniformity of the plasma state, which was a disadvantage of high-frequency plasma as mentioned earlier, and it is good. It is possible to get familiar with the material and obtain one with J-wearing strength.

As the hydrocarbon, all hydrocarbons can be used, including paraffinic hydrocarbons such as methane, ethane, propane, and butane, olefinic hydrocarbons, acetylene, diolefinic hydrocarbons, and aromatic group hydrocarbons.

The ratio of FI2 to hydrocarbon is 5 to 1,000; if it is less than 5, graphite will precipitate, and if it is more than 1,000, no diamond will be produced.

Thermionic emitting material is preferably a filament such as W, Ta, λ(0, La B e, etc.) The temperature of the thermionic emitting material is +200
Diamonds do not form under 'cJ, so a temperature above this temperature is preferable, preferably 1500°C or above.

Further, diamond does not form when the surface temperature of the substrate is below 30σC and above 1100°C.

The pressure inside the furnace is preferably 0.1 Torr-10, Torr.

Next, an apparatus for implementing the present invention is shown in FIG.

■ is a filament (thermionic emitting material), ■ is a substrate, ■ is a substrate support, ■ is a reaction furnace, ■ is a heating furnace, ■ is a coil or electrode, ■ is a high frequency massaging box, ■ is a high frequency power supply,
■ is - gas inlet pipe, [phase] is exhaust device, 0■ is hydrocarbon gas (:lli supply device, (ri is hydrogen gas supply device, 0~
0Q is a valve.

Q) is located behind the substrate (relative to the gas flow) and heats the surface of the substrate by Calo (2), thereby generating plasma.

Also, depending on the case, it is not always safe to install it at the rear, and it may be possible to place it in front of the substrate. This is not desirable because the problem of /f appears.

In this case, the important point is that high-frequency plasma is generated in the furnace, and the excited state of hydrocarbons and hydrogen due to thermal electron radiation can be maintained for a longer period n5.

[Phase] is used to control the pressure inside the furnace.

An example is shown below.

(Example 1) A WC-6% Co cemented carbide was used as a base material and charged into a furnace, and H2 plasma was generated by using H2 gas as a reaction gas at 1000 cc/min and CH4 gas at 10 mA.

The thermoelectron emitting material was W filament (W filament) and the surface temperature was 2000°C. The substrate is heated to pJ ((5
The reaction was carried out for 4 hours (00°C).

After the reaction, the surface of the substrate was examined, and it was found that 2 μm of diamond film had been formed. The uniformly coated zone was in the region of less than 30 mm away from the filament.

When the plasma generation was stopped and the reaction was carried out, the substrate could be coated only to a depth of 1 Omm from the point 30" or 2K away from the filament.

Diamond was tested using electron beam diffraction and laser Raman spectroscopy, but peaks unique to diamond were obtained in both cases.

For this trial, A+-11% 81 alloy was cut.

Y conditions are V2500m/2ain, f = 0.1m
m/pv, , t=1. (hnm, T=I5
It was a minute. Base shape i1 JIS i'PP322
Toshi and Himaki pieces are untreated VIIC-6%Co (same base material) alloy.

The substrate on which the diamond film was cured showed almost no wear.

(Example 3) The Si3N4-based ceramics obtained in (Example 3) were charged into a furnace, and the mixed gas was 500 cc/min of l-12 gas and 500 cc/min of C114 gas.
It was introduced at a flow rate of 0 cc/min, and the total pressure in the furnace was 2'l'', or
Let it be r again.

The high frequency was used to generate l-12 plasma with the anode's pressure set to 7 KV, anode current IA, and grid current + OQmA.

i'hO,, As a thermionic emitter which is a doped W filament, the surface temperature of this filament is set to 2200°.
To C! I heated it up.

The surface of the substrate was heated in a furnace to 600 DEG C., and furnace temperature analysis revealed that -J'Jq was 11°.

loo+ from the surface of the diamond film (one grain, 30III+l1i1' than the filament)
A diamond film was formed up to a diameter of 1 nmσ).

The film thickness was 1.Xμ.

When the reaction was carried out under the same conditions of fl''fi in a furnace without applying plasma, diamond was produced at a distance of 30 mrrJ9 from the filament for a distance of lom+n.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of an example of an apparatus for carrying out the method of the present invention. ■ Filament (challenge tlb, child radiation A) (substrate ■ Substrate support stand ■ Reaction section (5) heating section ■ Coil or i'j electric orange ■ High frequency Matsushi leg box (marked high frequency power supply ■ Waste introduction tube OQυl air) Equipment side Hydrocarbon scum supply device 6-2 (Hydrogen gas supply device (n ~ (method for writing amendments to the slander procedure) March 27, 1980, Commissioner of the Patent Office Kazuo Wakasugi), Patent application for indication of the case in 1982 -223066 No. 2, Name of the invention: Low-pressure synthesis method for diamonds 3, Relationship to the amended case Patent applicant: 5-2 Otemachi-chome, Chiyoda-ku, Tokyo (626) Mitsubishi Metals Corporation Representative Ken Nagano 5. Date of amendment order: February 28, 1980 6. Target of amendment: Specification IA of patent application filed on November 29, 1988 7.
, the content of the amendment: engraving of the drawing (no change in content).

Claims (1)

[Claims] A low-pressure method for synthesizing diamond, in which diamond is introduced in a controlled manner, activated by a heated thermionic emitter, and then brought into contact with a substrate heated to 300"C: ~1100°C to cause diamond to react and form on the substrate.